Disposable diaper

ABSTRACT

A disposable diaper ( 1 ) comprising a liquid permeable topsheet ( 2 ), a liquid impermeable backsheet ( 3 ), and liquid retentive absorbent members ( 41 ), ( 42 ), and ( 43 ) interposed between the two sheets, wherein the absorbent members ( 41 ) ( 42 ), and ( 43 ) are disposed in series in the direction of from the rear portion (B), through the crotch portion (A), to the front portion (C), an elastic member is disposed in its stretched state on both sides of the series of the absorbent members, and 
     the absorbent members ( 41 ), ( 42 ), and ( 43 ) are arranged such that a gap is produced between any adjacent two of them when the diaper is stretched flat and that any adjacent two of the absorbent members come into close contact when the diaper is worn.

TECHNICAL FIELD

The present invention relates to a disposable diaper providing a snugfit with little bagging of its absorbent member while worn.

BACKGROUND ART

A disposable diaper generally has a one-piece, vertically long absorbentmember disposed on an area from the rear portion, through the crotchportion, to the front portion. Elastic members are usually arranged onthe leg portions to give an improved fit to wearer's legs for leakageprotection.

In conventional disposable diapers, the leg portions contract withcontraction of the elastic members whereas the absorbent member is notso contractible in its longitudinal direction because of its stiffness.As a result, the absorbent member sometimes becomes baggy (swellingoutward) by the excess length while worn, which can cause inconveniencessuch as liquid's staying in the crotch portion, overhydration, andleakage. Because so-called fitted type (tape type) disposable diapers,in particular, are generally folded widthwise and compression packagedin a bag as folded for distribution and sale, the absorbent member getsoddly creased and more liable to bagging out when the diaper is worn.

JP-A-11-216161 proposes a disposable diaper in which an absorbent coreis divided along imaginary lines extending in the diaper lengthdirection and also along imaginary lines perpendicular to thoseimaginary lines. The absorbent core has a particle layer made mainly ofa superabsorbent polymer and a fiber layer underlying the particlelayer. If absorption by the particle layer results in gel blocking,further transfer of liquid to the fiber layer would be hindered. Thedivision of the absorbent core aims to make the fiber layer capable ofdirect absorption from the side faces and to increase the totalabsorption area of the core. To achieve the aims, the gaps betweendivided sections of the core should be retained during use of thediaper. Therefore, the proposed disposable diaper is incapable ofpreventing bagging of the absorbent member and the resultantinconveniences while worn.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a disposable diaperproviding a snug fit with little bagging of its absorbent member whileworn.

The above object is accomplished by a disposable diaper of the presentinvention. The disposable diaper of the present invention has a liquidpermeable topsheet, a liquid impermeable backsheet, and a liquidretentive absorbent member interposed between the topsheet and thebacksheet. The disposable diaper of the present invention has aplurality of the absorbent members disposed in series in the directionof from the rear portion, through the crotch portion, to the frontportion of the diaper and also has an elastic member disposed in itsstretched state on both sides of the series of the absorbent members.The absorbent members are arranged such that a gap is produced betweenany adjacent two of the absorbent members when the diaper is stretchedflat and that the adjacent two of the absorbent members come into closecontact with each other when the diaper is worn.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic perspective view of a disposable diaper accordingto an embodiment of the present invention.

FIG. 2 is a plan view of the disposable diaper of FIG. 1 in itsstretched flat state.

FIG. 3 is a schematic cross-sectional view taken along line X-X in FIG.2.

FIG. 4 is a schematic cross-sectional view of the disposable diaper ofFIG. 2 in its worn state.

FIG. 5( a), FIG. 5( b), and FIG. 5( c) each show the form of the fixedend of standing gathers in the vicinity of the facing corners ofadjacent absorbent members; in which FIG. 5( a) shows that of thedisposable diaper of FIG. 1, and FIG. 5( b) and FIG. 5( c) give otherexamples.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail with reference to itspreferred embodiment.

As shown in FIGS. 1 to 3, a disposable diaper 1 according to theembodiment contains a liquid permeable topsheet 2, a liquid impermeablebacksheet 3, and a liquid retentive absorbent members 41 to 43 that aredisposed between the two sheets. The disposable diaper 1 has a crotchportion A, which is positioned in the lengthwise middle of the diaperand adapted to be applied to the crotch of a wearer, and a rear portionB and a front portion C which are in the rear and the front of thecrotch portion A, respectively.

The diaper 1 is a so-called fitted (tape type) diaper having a fasteningtape 5 on both sides of the rear portion B and a landing zone 6 forreceiving the fastening tapes 5 on the outer side of the front portionC.

The diaper 1 has arc-shaped sides in its crotch portion A to make theshape of a sandglass (with the lengthwise middle narrowed) as a whole.The backsheet 3 has the same sandglass-shaped contour as the diaper. Thetopsheet 2 is superposed on the widthwise middle region of the backsheet3 with the absorbent members 41 to 43 sandwiched therebetween. Thebacksheet 3 extends outward from both longer side edges of the topsheet2. A sheet 92 for forming standing gathers (described infra) is joinedon each side extension of the backsheet 3.

The diaper 1 has three absorbent members 41, 42, and 43. As depicted inFIG. 2, the absorbent members 41 to 43 are arranged in series in thedirection of from the rear portion B, through the crotch portion A, tothe front portion C. The direction of “from the rear portion B, throughthe crotch portion A, to the front portion C” is the same as thedirection of “from the front portion C through the crotch portion A, tothe rear portion B”. In the case of a fitted diaper of tape type that isalmost a rectangle longer than wide like the diaper 1, that direction isdefined to be a diaper length direction.

As shown in FIG. 2, the three absorbent members 41 to 43 are rectanglesin their plan views and substantially equal in dimensions in thethickness and diaper width directions. The dimension of the absorbentmembers in the diaper length direction descends in the order of 41, 43,and 42. The boundary between the absorbent members 41 and 42 ispositioned at almost the middle of the crotch portion A (i.e., almostthe middle of the diaper length), and that between the absorbent members42 and 43 is slightly apart from that middle position toward the frontportion C.

An elastic member 7 is arranged in its stretched state on both sides ofthe series of the absorbent members 41 to 43, i.e., in the diaper lengthdirection. There are a plurality of the elastic members 7 on each sideof the diaper along the diaper length direction. The elastic members 7are arranged along both sides of the absorbent members 41 to 43 in theareas slightly outside both the side edges of each absorbent member andfixed with an adhesive between the backsheet 3 and the respective sheets92.

The elastic members 7 are disposed over a length between the absorbentmember 41 that is the nearest to the waist edge 11 of the rear portion Band the absorbent member 43 that is the nearest to the waist edge 12 ofthe front portion C. In the present embodiment, the elastic members 7also serve as elastic members for leg gather formation. That is, theelastic members 7 are disposed on the leg portions around wearer's legsto form leg gathers in the leg portions.

The absorbent members 41 to 43 are disposed such that a gap is producedbetween any two of them when the diaper is stretched flat and that anytwo of them come into close contact with each other while the diaper isworn.

Specifically, there is a gap P between the absorbent members 41 and 42and between the absorbent members 42 and 43 when the diaper 1 isstretched flat as depicted in FIG. 2. While the diaper 1 is worn, on theother hand, the absorbent members 41 and 42 are brought into closecontact, and the absorbent members 42 and 43 are brought into closecontact, both by the contracting force of the elastic members 7.

That the adjacent absorbent members come into close contact while thediaper is worn does not mean that they should be always in close contactwith each other while the diaper is worn. Where the absorbent membersare each made of a fiber aggregate and/or a superabsorbent polymer, theymay come into direct contact with each other or indirect contact via anonwoven fabric 8, tissue paper or any other sheeting.

According to the present embodiment, the leg portions around wearer'slegs contract by the elastic members 7 to provide a snug fit to thelegs. At the same time, the widthwise middle region of the diaper 1where the absorbent members 41 to 43 are disposed also gives a good fitto the wearer's crotch without causing the absorbent members to bag out.Thus, such inconveniences as liquid's staying in the crotch portion,overhydration, and leakage can be prevented.

In addition, since the adjacent absorbent members are brought intointimate contact while the diaper is worn, a combination of theabsorbent members is equal or superior to a one-piece absorbent memberlonger than wide in absorptivity and leakproofness.

In order to enjoy enhancement of the above-described effects, thedistances L1 and L2 (see FIG. 2) between the adjacent absorbent membersare preferably 3 to 20 mm, more preferably 5 to 10 mm, when the diaperis stretched flat. The facing edges of any adjacent two of the absorbentmembers are preferably parallel to each other. For the same purpose, theelastic members 7 are preferably disposed over at least a length frompart of the absorbent member 41 to part of the absorbent member 43,either with an overlap with the absorbent members 41 to 43 or in thearea very near to the absorbent members 41 to 43. Where the elasticmembers 7 are disposed near the absorbent members, the smallest distanceL3 (see FIG. 3) between the side edge of every absorbent member and theelastic members 7 is preferably 50 mm or shorter, more preferably 30 mmor shorter.

The absorbent members 41 to 43 of the diaper 1 according to the presentembodiment are each made of a fiber aggregate and/or a superabsorbentpolymer. As shown in FIG. 3, opposite side faces 44 extending in thediaper length direction and the skin-facing surface 45 (the surface onthe side that is applied to the wearer's body) of every absorbent memberare covered with a sheet of nonwoven fabric 8 that overlies to bridgethe plurality of the absorbent members. The nonwoven fabric 8 iswater-hydrophilic in a part 81 of the area covering the skin-facingsurface 45 of each absorbent member, i.e., the diaper width middle areaindicated by the dotted line. The nonwoven fabric 8 is water-repellentin the other area, i.e., the area covering the opposite side faces 44and the skin-facing surface 45 except the part 81, of every absorbentmember.

In the diaper 1 of the present embodiment, the gaps between the adjacentabsorbent members contract following the contraction of the elasticmembers. Therefore, the material bridging the gaps and covering theabsorbent members is required to be strong and flexible. Suchrequirements are sufficiently satisfied by using nonwoven fabric insteadof tissue paper as a material covering the absorbent members made of afiber aggregate and/or a superabsorbent polymer.

With the opposite side areas of the skin-facing surface and the oppositeside faces of every absorbent member being covered with the waterrepellent part of the nonwoven fabric as in the diaper 1 of the presentembodiment, there is obtained an advantage that once absorbed liquidhardly flows back. For application to elder infants who pass their urineat high flow rates, the rate of absorption may be too slow to keep upwith the flow rate of urination. Therefore, the diaper according to thisembodiment is suited for application to young infants.

The above-described nonwoven fabric 8 may be replaced with a nonwovenfabric that is water-hydrophilic in the area covering the entireskin-facing surface 45 of every absorbent member and water-repellent inthe area covering the opposite side faces 44 of every absorbent member.In this case, the water-repellent area covers only the side faces of theabsorbent members so that the absorbent members exhibit waterwettability over a wider area. Accordingly, the diaper of this type isfit for elder infants or adults who pass a relatively large amount ofurine. In the diaper 1, the non-skin-facing surface 46 of everyabsorbent member is covered with a second nonwoven fabric 8′ bridgingall the absorbent members.

The nonwoven fabric having a water-hydrophilic area and a waterrepellent area can be obtained by, for example, rendering a part ofnonwoven fabric made of hydrophobic fiber water-hydrophilic by any knownprocessing or making a part of nonwoven fabric made of hydrophilic fiberwater-repellent by any known processing. Any nonwoven fabric produced byvarious processes can be used as a covering material. To satisfy bothrequirements for strength and flexibility, and the like, it is advisableto use SMS nonwoven (three-layered laminate having aspunbond/meltblown/spunbond structure), spun-bonded nonwoven, orheat-rolled nonwoven.

The diaper 1 of the present embodiment has standing gathers 9, 9 on bothside portions thereof extending in the direction of from the rearportion B, through the crotch portion A, to the front portion C, i.e.,in the diaper length direction. In more detail, the opposing standinggathers 9 are formed by fixing the respective standing gather-formingsheets 92 having the respective elastic members 91. Each sheet 92 isfixed along a longer side of the diaper such that it may cover an areaof the topsheet 2 inward and outward about a longer side edge of thetopsheet 2. Each sheet 92 is fixed to the topsheet 2 at a predeterminedposition in the diaper width direction by a joint 93. The joint 93 ismade by known means, such as heat seal or an adhesive. The part fixed bythe joint 93 is the fixed end 94 of the standing gathers. The area ofeach sheet 92 outside the fixed end 94 is fixed onto the topsheet 2 orthe backsheet 3. The area of each sheet 92 inside the fixed end 94 andnear each of the opposite lengthwise ends of the diaper are fixed ontothe topsheet 2.

In the diaper 1 of the present embodiment, the fixed end 94 of thestanding gathers 9 on each side is not linear but wavy along the diaperlength direction as shown in FIG. 2. As shown in FIG. 5( a), a part ofthe fixed end 94 depicts a projection sticking toward the widthwisemiddle of the diaper in each of regions D and E that are in the vicinityof the facing corners of the adjacent absorbent members. Morespecifically, the fixed end 94 of the standing gathers 9 extendssubstantially in the diaper length direction but, in the region D nearthe facing corners of the absorbent members 41 and 42 and the region Enear the facing corners of the absorbent members 42 and 43, the positionof the fixed end 94 is shifted toward the widthwise middle of thediaper. As a result, when the diaper is stretched flat and seen from theside of its topsheet 2 the fixed end 94 is curved inward to the diaperwidthwise middle to depict a projection. What is meant by the term“wavy” as used in the present invention is not limited to “having astrictly sinusoidal waveform” but includes “having a substantiallysinusoidal waveform, such as the form shown in FIG. 5( b)”.

In a diaper having a plurality of absorbent members arranged in series,diffusion of liquid in the diaper width direction is accelerated so thatthe demand for leakproofness of the standing gathers is stricter.Furthermore, liquid is apt to run in the diaper length direction betweenthe side edges of the absorbent members and the standing gathers. Hence,by the standing gathers of which the fixed end is arranged in a wavyform with inward projections in parts as described above, the liquidflowing outward in the diaper width direction is returned inward in thediaper width direction, and the liquid running in the diaper lengthdirection is once blocked and helped to be absorbed in the vicinity ofthe urination point of a wearer. Leakage in both the diaper width andlength directions can be thus prevented effectively.

In the diaper 1 according to the present embodiment, the fixed ends 94of the opposing standing gathers 9 intrude between the adjacentabsorbent members, i.e., between the absorbent members 41 and 42 andbetween the absorbent members 42 and 43, as shown in FIG. 5( a).Therefore, the liquid running in the diaper length direction within thewidth of each absorbent member is effectively blocked by the standinggathers intruding from both sides. As a result, the standing gathersprovide enhanced prevention against leakage particularly leakage in thediaper length direction. The intrusion length L4 (see FIG. 5( a)) of thefixed end 94 between the adjacent absorbent members is preferably suchthat the total intrusion length on both sides (e.g., L4×2) is more than0% and not more than 10% of the width of the absorbent members (thedimension in the diaper width direction).

Materials making up the diaper 1 of the present invention will now bedescribed. The topsheet 2, the backsheet 3, the standing gather-formingelastic members 91, and the standing gather-forming sheets 92 can be ofany material chosen from among various kinds heretofore employed inabsorbent articles including disposable diapers and sanitary napkins.

The fiber aggregate making part of, or the whole of, the absorbentmembers 41 to 43 may be either a nonwoven fabric or a fiber web.Constituent fibers include pulp fiber, cellulosic fibers such as rayonand cotton, polyolefin fibers such as polyethylene and polypropylene,polycondensation fibers such as polyester (e.g., polyethyleneterephthalate) and polyamide, and vinyl polymers such as polyvinylchloride and polyvinyl acetate. The fibers may be single-component fiberor conjugate fiber of side-by-side configuration, sheath-coreconfiguration, etc.

Any known superabsorbent polymer can be used to make part of, or thewhole of, each of the absorbent members 41 to 43. Examples of usefulsuperabsorbent polymers are sodium polyacrylate, an acrylic acid-vinylalcohol copolymer, crosslinked sodium polyacrylate, a starch-acrylicacid graft copolymer, an isobutylene-maleic anhydride copolymer or asaponification product thereof, and polyaspartic acid.

Each of the absorbent members used in the present invention may be madesolely of a fiber aggregate or a superabsorbent polymer but ispreferably made of a combination of a fiber aggregate and asuperabsorbent polymer. The superabsorbent polymer can be present asdispersed in the fiber interstices of a fiber aggregate or sandwiched inbetween nonwoven fabrics or fiber webs made of a fiber material.

Materials of the elastic members 7 include synthetic rubber, naturalrubber, and Spandex and the like. The form of the elastic members 7includes not only yarn but tape and film and the like.

The present invention is not construed as being limited to theabove-mentioned embodiment, and various changes and modifications can bemade therein without departing from the spirit and scope thereof.

For example, while the above-described diaper 1 has three absorbentmembers laid out in series, the diaper can have two or more than threeabsorbent members arranged in series. All the absorbent members used inone diaper may be equal in dimension in the diaper length direction, orat least one of them may be different in dimension in the diaper lengthdirection. The same applies to the thickness and the dimension in thediaper width direction.

The part of the standing gathers' fixed end located in the vicinities ofthe facing corners of adjacent absorbent members can have the form shownin FIG. 5( b) or FIG. 5( c) instead of the form shown in FIG. 5( a).

In order to bring the adjacent absorbent members into close contact moresurely, a second elastic member may be disposed in its stretched statein the diaper widthwise middle to extend in the diaper length direction,in addition to the elastic members 7 provided on both longer sides ofthe diaper. The number of the elastic member 7 arranged on the bothsides in the diaper length direction may be one on each side.

The disposable diaper according to the present invention may be ofpull-on type.

INDUSTRIAL APPLICABILITY

The disposable diaper of the present invention provides a snug fit withlittle bagging of its absorbent member while worn.

1. A disposable diaper comprising a liquid permeable topsheet, a liquidimpermeable backsheet and three liquid retentive absorbent membersinterposed between the topsheet and the backsheet, said three absorbentmembers being disposed in series in the direction of from the rearportion, through the crotch portion, to the front portion of the diaper,and wherein the length of the three absorbent members descends in theorder of the rear portion absorbent member, the front portion absorbentmember and the crotch portion absorbent member, elastic members beingdisposed in a stretched state on both sides of said series of said threeabsorbent members, such that when said diaper is worn, the elasticmembers are disposed on the leg portions around the wearer's legs, andwherein the elastic members are disposed longitudinally on both lateralsides of the disposable diaper from the rear portion absorbent member tothe front portion absorbent member, said absorbent members beingarranged such that a gap, wherein said gap extends in a width directionof said diaper, is produced between any adjacent two of said threeabsorbent members when the diaper is stretched flat and that anyadjacent two of said three absorbent members come into close contactwith each other when the diaper is worn; and wherein a boundary betweenthe absorbent members in the rear and crotch portions is positioned atabout the middle of the diaper length, and a boundary between theabsorbent members in the crotch portion and front portion is slightlybefore the middle of the diaper length and toward the front of thediaper.
 2. The disposable diaper according to claim 1, wherein each ofsaid absorbent members comprises a fiber aggregate and/or asuperabsorbent polymer, the opposite side faces of each of saidabsorbent members which extend in the diaper length direction and theskin-facing surface of each of said absorbent members are covered with asheet of nonwoven fabric which bridges said absorbent members, and saidnonwoven fabric is water-hydrophilic in a part or the whole of the areacovering said skin-facing surface of each of said absorbent members andis water-repellent in the area covering said opposite side faces of eachof said absorbent members.
 3. The disposable diaper according to claim1, wherein standing gathers are provided on both sides of the diaperalong the direction of from the rear portion, through the crotchportion, to the front portion of the diaper, said standing gathers oneach side being formed by fixing a standing gather-forming sheet havingan elastic member along each of the longer sides of the diaper such thatsaid sheet covers an area of the topsheet inward and outward about eachof the longer side edges of the topsheet.
 4. The disposable diaperaccording to claim 1, wherein standing gathers are provided on each sideof the diaper along the direction of from the rear portion, through thecrotch portion, to the front portion, the fixed end of said standinggathers on each side depicting a wavy line, and part of said fixed enddepicting a projection toward the widthwise middle of the diaper in thevicinity of the facing corners of any adjacent two of said absorbentmembers.
 5. The disposable diaper according to claim 4, wherein saidpart of said fixed end intrudes between said any adjacent two of saidabsorbent members.